Technical Abstract: A 5-year field study evaluated 42 sunflower (Helianthus annuus L.) accessions, 25 breeding lines, and 40 interspecific crosses for resistance to infestation by naturally occurring populations of the sunflower moth, Homeosoma electellum (Hulst) (Lepidoptera: Pyralidae). Germplasm with resistance to infestation and damage from larval feeding by the sunflower moth was determined from this research. Accessions PI 175728 and PI 307946 had < 3% feeding damage per head in all three years of testing. Some interspecific crosses showed evidence of resistance; PAR 1673-1 had < 2% seed damage in 2002 and 2003 and < 3% in 2005. PRA PRA 1142 sustained less than 3% seed damage and STR 1622-1 had < 2% seed damage in three years of trials. Breeding lines with potential resistance included 01-4068-2, which had the least amount of seed damage per head in 2002 (< 1%) and in 2003 averaged only 2% damage. Line 01-4080-1, with < 1% damage in 2002 and in 2003, was the lowest in the trial. Hybrid ‘894’ was included as a standard check; however, it consistently had among the lowest average seed damage from H. electellum feeding among the germplasm evaluated. Our investigation showed potential in developing resistant genotypes for the sunflower moth to reduce seed feeding injury and to prevent yield loss for the sunflower producer. The development of germplasm with host plant resistance would provide another tool in an integrated pest management approach for H. electellum. Additional effort is in progress to use the identified lines to introgress resistance genes into cultivated sunflower through conventional breeding facilitated by the use of marker-assisted selection.